Stability of anionic liposome-cationic polymer complexes in water-salt media

Laser microelectrophoresis, dynamic light scattering, and fluorescence and UV spectroscopy are employed to study poly-N-ethyl-4-vinylpyridinium bromide adsorption on the surface of bilayer lipid vesicles (liposomes) formed from mixtures of anionic phosphatidyl serine and electroneutral phosphatidylcholine. It is established that polycation adsorption is accompanied by the neutralization of charges on liposomes and their aggregation. The subsequent addition of a low-molecular-weight salt (NaCl) solution to suspensions of complexes causes them to dissociate into their initial components, while the stability of the complexes with respect to the salt action increases with the fraction of the anionic lipid in the liposome membranes. The data obtained are interpreted from the position of the formation-disintegration of a molecular capacitor, the charge of which is generated by spatially separated anionic lipids located in the bilayer membrane and cationic units of the adsorbed polyamine.     

Generation of the third harmonic of near IR femtosecond laser radiation tightly focused into the bulk of a transparent dielectric in the regime of plasma formation

The generation of the third harmonic of femtosecond laser radiation with a wavelength of 1.24 μm tightly focused into the bulk of fused silica was simulated numerically for the regime with light intensity of 3 × 10¹³ W/cm², which is extreme for solid bodies. The efficiency of third harmonic generation (THG) was found to be restricted to 0.1% in the regime of plasma formation. This is determined by two competitive processes: a decrease of THG efficiency due to an increase of wave detuning and an increase of THG efficiency due to a growth of focusing asymmetry. In an isotropic medium, determination of the threshold of plasma formation by use of the third harmonic signal is shown to be a more sensitive method as compared with the standard scheme of nonlinear transmittance detection.     

Synthesis of Polyampholyte Janus-like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization

Controlling the distribution of ionizable groups of opposite charge in microgels is an extremely challenging task, which could open new pathways to design a new generation of stimuli-responsive colloids. Herein, we report a straightforward approach for the synthesis of polyampholyte Janus-like microgels, where ionizable groups of opposite charge are located on different sides of the colloidal network. This synthesis approach is based on the controlled self-assembly of growing polyelectrolyte microgel precursors during the precipitation polymerization process. We confirmed the morphology of polyampholyte Janus-like microgels and demonstrate that they are capable of responding quickly to changes in both pH and temperature in aqueous solutions.     

Structural Anisotropy of Amorphous Silicon Films Modified by Femtosecond Laser Pulses

It is demonstrated that the surface-relief orientation in the form of one-dimensional gratings with a period of 1.20 ± 0.02 μm formed under processing of hydrogenated-silicon films by femtosecond laser pulses (1.25 μm) with an energy density of 0.15 J/cm² is determined by the direction of the polarization vector of the radiation and total laser exposure. Based on the results of the analysis of Raman spectra, the presence of a nanocrystalline phase of silicon with a volume fraction between 15 and 67% (depending on processing conditions) is detected. The observed processes of micro- and nanostructuring are caused by excitation of the surface plasmon–polaritons and nanocrystallization in the near-surface region in the field of high-power femtosecond laser pulses, respectively. In addition, formation of polymorph modifications of silicon Si-III and Si-XII under femtosecond laser processing with a number of pulses exceeding 500 is discovered. Anisotropy of the Raman signal for the above polymorph modifications is revealed.     

The synthesis of N-substituted β-(5-amino-2-furyl) nitroolefins

Studying nucleophilic substitution reactions in a number of β-(5-halo-2-furyl) nitroolefins (I) with secondary amines, we have shown for the first time the possibility of synthesizing the previously unknown N-substituted β-(5-aminofuryl)nitroolefins (II). We have found that the smoothest substitution reaction takes place in the case of the 5-halo-furylnitropropenes (I, R=CH₃) with morpholine and methylaniline when their alcoholic solutions are heated.     

Performance of Single-Chamber Solid Oxide Fuel Cells Based on Ni and Ni–Cu Alloy Anodes and Fed with a Methane–Air Mixture

Kinetics and Catalysis - The electrochemical characteristics of Ni|YSZ|LSM and Ni–Cu|YSZ|LSM single-chamber solid oxide fuel cells fed with a methane–air mixture ([CH4]/[O2] molar ratio...     

Nanostructured ultrathin films obtained by the spreading of diblock copolymers on a surface

We propose a theory of nanopattern formation in ultrathin films obtained by the spreading of A-B diblock copolymers on a surface. A blocks are strongly adsorbed (spread) on the substrate, and the strength of the adsorption can be varied. B blocks are incompatible with the substrate, but they can spread atop the layer of the A blocks. We predict disk-shaped micelles ordered with hexagonal symmetry and parallel stripe-shaped micelles and bilayers to be stable. The type of resulting structure and its geometrical parameters depend on the composition of the copolymer and interaction parameters. We interrelate these results with those obtained for the case of the spreading of both blocks on the substrate, and we construct a unified phase diagram.     

Triosmium cluster with the bridging aminooxime derivative of pinane: Synthesis,crystal structure and conformational analysis

The reaction of 1R,2R,5R-2-dimethylamino-2,6,6-trimethylbicyclo[3.1.1]heptane-3-one oxime (pinaneoxime) with Os₃(CO)₁₀(NCMe)₂ was used to synthesize the (μ-H)Os₃(μ-κ¹-O-N=C₁₂H₂₁N)(CO)₁₀ cluster with coordination of the ligand through the oxime O atom and invariable terpenoid structure. The structure of the synthesized cluster was determined by X-ray diffraction analysis. The theoretical conformational analysis of the above cluster in a solution and in crystal state was performed by a combined MM3/MERA method. The rotation of a ligand about the O(1)-N(2) bond was found impossible due to a high energy barrier (E > 550 kJ/mol).     

Block Copolymer Based Molecular Motor

We propose a model of molecular motor based on diblock copolymer strongly adsorbed on a patterned surface. One of the blocks of the copolymer is modeled as field responsive. It is shown that time‐periodic collapse‐readsorption of the responsive block leads to the directed motion (reptation) of the molecule along the “track” provided by the surface pattern. Both the Langevin dynamics (LD) technique of computer simulation for the bead‐spring model and numerical solution of the Newton equations of a simplified (toy) model of the copolymer are used. The physical reason of directionality of the motion is shown to be an anisotropy of the friction of the molecule with the surface.